# QuickNode JSON-RPC Proxy — Arbitrum Sepolia

> QuickNode JSON-RPC Proxy — Arbitrum Sepolia is a paid API for AI agents from x402.quicknode.com, paid per call via x402, $10/call, status unknown (last checked 2026-09-14).

Proxies JSON-RPC calls to the Arbitrum Sepolia testnet via QuickNode's blockchain node infrastructure

## Facts

- Endpoint: POST https://x402.quicknode.com/arbitrum-sepolia/
- Price: $10/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/quicknode-a81f81a5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_1aqGmASRdO0iNluIFhG81

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability quicknode-a81f81a5 -d '<json body>'
```

Example prompt: Call eth_getBalance on Arbitrum Sepolia for address 0xAbCd1234... at block 'latest' using QuickNode's JSON-RPC proxy.

## When to prefer this

Use this endpoint when you need to interact specifically with the Arbitrum Sepolia testnet — for example, testing smart contracts, querying testnet balances, or simulating transactions before mainnet deployment. Prefer this over generic RPC providers when you need a reliable, pay-per-call QuickNode-backed node without managing your own infrastructure.

## Known failure modes

- Invalid JSON-RPC method name returns error code -32601 (method not found)
- Malformed params array returns error code -32602 (invalid params)
- Payment not included or insufficient returns HTTP 402
- Network congestion on Arbitrum Sepolia may cause delayed responses
- Testnet node downtime returns HTTP 503 or connection error
- Requesting finalized state for a very recent block may return null

## How this service works

JSON-RPC proxy — arbitrum-sepolia

## Output

Returns a standard JSON-RPC 2.0 response object containing the result of the requested method (e.g. block data, balance in hex wei, transaction receipt, contract return value) or an error object with code and message if the call fails.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "jsonrpc",
  "method"
 ],
 "properties": {
  "id": {
   "type": [
    "number",
    "string"
   ],
   "description": "Request identifier"
  },
  "method": {
   "type": "string",
   "description": "JSON-RPC method name (e.g., eth_blockNumber, eth_call)"
  },
  "params": {
   "type": "array",
   "description": "Method parameters"
  },
  "jsonrpc": {
   "type": "string",
   "const": "2.0"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "id": {
   "type": [
    "number",
    "string"
   ]
  },
  "error": {
   "type": "object",
   "properties": {
    "code": {
     "type": "integer"
    },
    "message": {
     "type": "string"
    }
   }
  },
  "result": {
   "description": "RPC result (type varies by method)"
  },
  "jsonrpc": {
   "type": "string",
   "const": "2.0"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/quicknode-a81f81a5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.quicknode.com](https://www.zero.xyz/host/x402.quicknode.com/llms.txt)